Industrial ion exchange resins are used for a variety of processes, ranging from water softening to metal mining operations. When used to extract ions from complex or dirty mixtures, the resins can become fouled with suspended solids or materials that precipitate in the ion exchange resin during processing. Ion exchange resin fouling is a significant problem in the industrial setting, given the large quantities and high unit cost of the resins.
Iron fouling is a widespread and difficult problem for industrial ion exchange resins. Fouling of ion exchange resins by iron can occur by deposition of suspended iron-containing solids or by precipitation, such as that due to oxidation of iron compounds in solution.
Geothermal brines present a particular problem with respect to fouling of ion exchange resins. These brines, which can be obtained by drilling into geothermal formations, are extremely hot and under great pressure. Although sodium, potassium and calcium chlorides comprise the bulk of the dissolved material, the brines contain large quantities of other dissolved ions, including iron, manganese, silicates, zinc, and other metals. Some processes for recovery of commercially valuable metals from geothermal brines incorporate ion exchange "capture" steps, which can semi-selectively bind the metal of interest. However, if the brine contains large amounts of iron and/or calcium, either as suspended solids or dissolved salts, these metals can contaminate the ion exchange resin, reducing the capacity and lifespan of the resin.
Some preparations are commercially available for removing iron fouling. The product Iron Out.RTM., a mixture of sodium dithionite and sodium bisulfite, (Iron Out, Inc., Ft. Wayne, Ind.) can be effective for minor iron fouling of ion exchange resins. However, heavy iron fouling requires more stringent cleaning products and/or procedures.
Accordingly, there is a need in the art for a simple, highly efficient method for removing fouling from ion exchange resins.